A self-powered artificial optoelectronic synapse based on lead-free organic–inorganic hybrid molecular ferroelectric [C₄N₂H₁₄][BiI₅]

This work demonstrates a self-powered artificial optoelectronic synapse based on the lead-free organic–inorganic hybrid molecular ferroelectric [C₄N₂H₁₄][BiI₅] (BDA-BiI₅). Leveraging its pronounced room-temperature ferroelectricity and efficient ferroelectric photovoltaic effect, the device operates without any external bias, enabling ultralow power consumption. Under light pulse stimulation, it successfully emulates essential synaptic plasticity behaviors, including paired-pulse facilitation, short- and long-term plasticity, and the transition from short-term to long-term memory. The fabricated artificial synapse also exhibits spike-rate-dependent plasticity, which is utilized to construct a high-pass filter for image sharpening. Furthermore, the device demonstrates associative learning capability through a Pavlovian conditioning experiment. These results highlight BDA-BiI₅ as an environmentally benign and multifunctional material for neuromorphic hardware, offering a promising route toward energy-efficient, bio-inspired visual perception systems.